Final Words

For the first time since late 2008, I went back to using a machine where a hard drive was a part of my primary storage - and I didn’t hate it. Apple’s Fusion Drive is probably the best hybrid SSD/HDD solution I’ve ever used, and it didn’t take rocket science to get here. All it took was combining a good SSD controller (Samsung’s PM830), with a large amount of NAND (128GB) and some very aggressive/intelligent software (Apple’s Core Storage LVM). Fusion Drive may not be fundamentally new, but it’s certainly the right way to do hybrid storage if you’re going to do it.

It seems that Fusion Drive is really made for the user who doesn't necessarily have a ton of applications/data, but does have a reasonable sized media collection. For that user, Fusion Drive should be a reasonable approximation of a well managed SSD/HDD setup with your big media files going to the HDD and everything that you launch frequently living on the SSD. I’m always going to ask for a larger cache, but I do believe that 128GB is a good size for most client workloads and usage models today. For me in particular I’d probably need a 256GB cache for Fusion Drive to win me over, but I understand that I’m not necessarily the target market here.

The real question is whether or not it’s worth it. I’m personally a much bigger fan of going all solid state and manually segmenting your large media files onto HDD arrays, but perhaps that’s me being set in my ways (or just me being right, not sure which one). Fusion Drive doesn’t do anything to mitigate the likelihood that a hard drive will likely fail sooner than a good SSD, whereas if you go with an internal SSD and external (Thunderbolt or USB 3.0) HDD RAID array you can control your destiny a bit better. Unfortunately, in situations where Fusion Drive is a choice, you don’t often have that flexibility.

On the iMac, Apple limits your options quite a bit. You can either buy a hard drive or the Fusion Drive on the 21.5-inch model, there’s no standalone SSD option. There the choice is a no-brainer. If you’re not going to buy your own SSD and replace the internal HDD with it (or try to see if OWC’s rMBP SSD fits), then the Fusion Drive is absolutely right choice. You’re paying handsomely for the right ($250 for 128GB of NAND is very 2011), but if you’re not willing to crack open the iMac case this is really the only way to go.

For the 27-inch iMac the decision is similarly difficult. Apple does offer a standalone SSD option, but it’s for a 768GB model that will set you back $1300. All of the sudden that $250 Fusion Drive upgrade sounds a lot more reasonable.

On the Mac mini side the decision is far simpler. The Fusion Drive is only available on the $799 configuration (for $250) but so is a 256GB SSD upgrade for $300. As long as you’re ok with using an external hard drive for mass storage, here I’d go for the big standalone SSD. The usual caveat applies: this is only true if you’re not interested in cracking open the mini yourself and using a 3rd party SSD.

To make things simpler, I made bold the options I'd choose given Apple's current lineup in the table below. Note that this is still assuming you're not going down the DIY route (if you do go down that path, buy the biggest SSD you can find and rely on some external mass storage for everything else):

Fusion Drive Options

Mac mini (2012)

21.5-inch iMac (2012)

27-inch iMac (2012)

Base System Cost

$799

$1299/$1499

$1799/$1999

1TB Fusion Drive

+$250

+$250

+$250

3TB Fusion Drive

-

-

+$400

Largest Standalone SSD

256GB
(+$300)

-

768GB
(+$1300)

I am curious to see how long of a roadmap Fusion Drive has ahead of it. Will NAND get cheap/large enough that even the iMac can move to it exclusively? Or will we end up with systems that have more than enough NAND to easily store everything but large media files for even the most demanding of power users? In less than a year Apple could double the size of the NAND used in Fusion Drive at no real change to cost. I suspect another doubling beyond that would be necessary to really make Fusion Drive a one size fits all, but then we're talking ~2 years out at this point and I don't know how static everyone's usage models will remain over that period of time. Go out even further in time, to the post-NAND era and there are some really revolutionary things that can happen to the memory hierarchy altogether...

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128 Comments

"The proportion of people who can handle manually segregating their files is much, much smaller than most of us realize"

I agreed with your post, but it always astounds me that commenters in articles like these need occasional reminders that the real world exists, and no, people don't care about obsessive, esoteric ways to deal with technological minutiae. Reply

Anybody else getting a bit of déjà vu? I recently saw a rehash of the compiler-vs-assembly (or perhaps, trick-playing to work around compiler-optimization bugs); the early comment was K&P, 1976.

Yes, anybody who knows what they're doing, and is willing to spend the time, can hand-tune a machine/storage system, better than a general-purpose algorithm. *I* have the combo SSD + spinner approach in my laptop, but would have saved myself MANY hours of fussing and frustration, had a good Fusion-type solution been available.

It'd be interesting to see how much time Anand thinks a person of his skill and general experience, would take to install, configure and tune a SSD+spinner combo, versus the time he'd save per month from the somewhat better results vis-à-vis a Fusion drive. As a very rough SWAG, I'll guess that the payback for an expert, heavy user is probably around 2–3 years, an up-front sunk cost that won't pay back because it'll be necessary to repeat with a NEW machine before the time.Reply

But then you end up with a SSD filled up with no longer relevant data and you need to figure out how to free up space again. A combo drive takes care of that for you and keeps the SSD filled to the brim with most of the data that gets used. You can download any games, start any big video editing project, and know that you are getting 50%-100% of the benefit of the SSD without worrying about managing segregated data. With a segregated setup you end up playing games from the HDD or editing video files that are on the HDD and sometimes see 0% of the benefit of the SSD. Fusion seems like the future.Reply

If you can divide your data up as OS, Apps, and Media, and OS + Apps fits on the SSD, then sure, it's not too bad.

Unfortunately, my Steam library is approximately 250 GBs... That alone would fill up most SSDs out there. And that's not even counting all my non-Steam games, which would help push most any SSD towards being totally full. If I'd bought too many recent games, it'd likely be quite a bit larger than that (AAA games seem to be ranging from 10-30 GBs these days).

Unless you sprung for a 500 GB SSD (which aren't exactly cheap, even today), you'd be having quite a pickle on your hands. Likely having to move most of the library manually to the HDD (which is a bit of a pain with Steam). Which means it's suddenly much more complicated than OS/Apps on SSD, and Media on the HDD. Especially since SSDs massively improve the load time of large games (unlike the impact it has on media).

And then there's the other examples I've already given: the artist I know that works on absurdly massive PSDs, and has many terabytes of them (what's the point of a SSD if it doesn't benefit your primary usage of a computer?), as well as my situation with VMs on my non-gaming machine (which actually has a SSD + HDD setup right now). A lot of people could probably do the divide you're talking about, but likely even more people could fit all their data in either a 128 or 256 GB SSD.Reply

Intel SRT is useful for everyone, there's no reason to look down on it. Could I sit there and manually move files back and forth between the SSD and HD? Sure. But why? Seriously, I have better things to do with my time then move around the program of the week between storage mediums. Last week I was using Metro 2033, this week is World of Tanks. Next week I might finish one of those run throughs of D:HR or Portal 2 that I left hanging. SRT takes care of all of that. This is 2013, an enthusiast class workstation should damn well be able to handle something as simple as caching, and it can. Enterprise class servers have been doing it for some time, so why isn't it good enough for a gameing rig?

My one complaint with RST is the cache size limit. Why would Intel even impose a limit?Reply

You're framing it in your own way so that only your solution works. Fail. Unnecessary stressing of the SSD? The better argument for most people would be putting that SSD to good use. Not trying to NOT use it.

It further isn't simply about putting the files where they go, and then be done with. Files are changed, updated, and if you're on multiple drives, copied back and forth. Some people don't want to deal with that. Actually, no one should want to do deal with that. There are only barriers with every person having their own thresholds to good solutions. Is it that hard to understand? Reply

Do you manually control the data in the 1st, 2nd level cache in your CPU too? There are plenty of decent caching algorithms created by very smart people. If the algorithms were that bad your CPU would be running very slow.

There should be no need for you to WASTE TIME moving crap around from drive to drive. The OS can know how often you use stuff, and whether the accesses are sequential, random, slow.

If Windows 8's Storage Spaces was more like Fusion Drive out of the box (or better even), us geeks would be more impressed by Windows 8.Reply

Having designed and built both computers and operating systems, I qualify as not naive. I'm interested in your assertion, therefore, that because I prefer letting the Fusion drive do the work that I must be lazy. You're making a judgement about how I should spend my time - that it's the best investment of my time to shuffle files about (non-trivial if I want the level of granularity a Fusion drive can offer, too) versus developing software or playing with my dog. It's interesting that you think you know me that well, regardless of the fact you're dead wrong.